1. Field of the Invention
The invention relates to a ice-filled cold storage means for repeat ed freezing and melting according to the preamble of the main claim. Cold storage means are e.g. used in refrigeration technology more particularly for vehicle cooling and air conditioning.
2. Description of the Prior Art
Vehicles are cooled and air conditioned, because in vehicles the air temperature and humidity can reach values which can impair the concentration of the vehicle driver, which can have an effect on the safety of road traffic. Another reason for air treatment is the comfort of the vehicle occupants and the requirements concerning transported goods.
Vehicles which are not in operation can normally not be cooled or air conditioned, because the cooling and air conditioning system is normally jointly supplied by the vehicle drive. Thus, particularly in the sun, such vehicles can be subject to considerable heating.
The heating effect is particularly critical if the vehicle is occupied and the engine cannot or may not be operated, so that the air conditioning and cooling system cannot function, because the drive is not available for it, which is e.g. the case with vehicles, on ferries, trucks and border crossings, in stop and go traffic or in the case of smog.
The problem of the invention is to provide for such cases a cold storage means. This makes it unnecessary to have a separate drive for cooling or air conditions systems and cooling and air conditioning can take place independently of the operation of the drive engine.
Ice is proposed for the storage means operation, particularly in the case of vehicles. Ice is produced from water or an aqueous solution or mixture (hereinafter merely referred to as water to facilitate understanding).
Among all standard single-component liquids water has both the highest specific heat capacity and the highest specific melting heat. In addition, water is inexpensive and safe. This makes water a suitable storage medium. Due to the high melting heat cold storage by ice (latent energy) is far superior to the storage of cold water (sensible energy) due to the lower volume or weight.
However, also in the ice range water has an abnormal behaviour compared with most other substances. In particular the volume rises in the case of ice formation and then decreases again on undercooling or subcooling the ice. If this volume change cannot be compensated by constructional measures (e.g. by a buffer volume), containers in which ice is produced could burst as a result of the ice pressure.
For weight and space reasons the cold storage means should also be small and light. This requires the complete freezing of the water to ice with the consequence that the volume change on freezing and melting is absorbed in an operationally safe manner.